1. Field of the Invention
The present invention relates to a constant vehicle speed maintaining device for a motorcycle. More particularly to a constant vehicle speed maintaining device for a motorcycle that is capable of canceling a constant vehicle speed state impairing the operating characteristics and without requiring a complex construction.
2. Description of Background Art
Motorcycles are known that have a constant vehicle speed maintaining device for maintaining the operating speed at a constant value for the purpose of alleviating the fatigue of the driver during operation, for cutting fuel cost by restraining vehicle speed variations, etc. In the constant vehicle speed maintaining device, it is required to cancel the constant vehicle speed state (hereinafter referred to as xe2x80x9ccruising statexe2x80x9d). Hitherto, it has been known to cancel the cruising state in response to the following actions: an action of returning a throttle grip against a turning force of an actuator which biases a throttle valve under the cruising state, an action of applying a brake to a front wheel or a rear wheel, an action of gripping a clutch lever, etc.
FIG. 4 illustrates a major part of a constant vehicle speed maintaining device which cancels a cruising state by detecting an action of returning the throttle grip. As illustrated in FIG. 4, a shaft (throttle shaft) 2 of a throttle valve (not shown) of an engine is disposed to penetrate a throttle body 1, and a throttle drum 3 and a throttle link 4 are attached to ends of the throttle shaft 2. A cable 6 for transmitting turning torques in acceleration and deceleration directions on a throttle grip 5 to the throttle drum 3 is wrapped around between the throttle drum 3 and the throttle grip 5.
In a cruising state a cancellation detector (cancel detector) 7, a first drum 71 connected with one end of the cable 6 and a second drum 72 connected with the other end of the cable 6 are disposed coaxially and turnably. A torsion spring 73 is provided between the first drum 71 and the second drum 72. The first drum 71 and the second drum 72 are turned as one body through the spring 73. A switch 8 is provided for detecting the cancellation of the cruising state when there arises such a displacement differential in the turning direction that the torsion spring 73 is deformed by not less than a predetermined amount, between the first drum 71 and the second drum 72.
On the other hand, the throttle link 4 is connected with a negative pressure type actuator 10 through a control cable 9. The negative pressure type actuator 10 is connected to the engine (not shown) through a solenoid unit 11, which regulates the introduction of engine negative pressure and atmospheric pressure to control the inside pressure. A diaphragm (not shown), disposed in the negative pressure type actuator 10, expands and contracts according to the inside pressure of the negative pressure type actuator 10, and the expanding and contracting actions are transmitted through the control cable 9 to the throttle link 4, whereby the throttle opening under the cruising state is controlled. The solenoid unit 11 is so controlled so as to respond to a setting signal for the cruising state and for maintaining the current vehicle speed. The solenoid unit 11 is controlled by an ECU 12 that includes a microcomputer. The ECU 12 is inputted with a vehicle speed signal, an engine revolution number signal (NE), cruising state setting and other control signals, a cruising state cancellation signal (cancel signal) is outputted from the switch 8, and the like.
During normal operation, the first drum 71 and the second drum 72 are turned synchronously with the rotation of the throttle grip 5, and the motion of the throttle grip is directly transmitted through the cable 6 to the throttle drum 3. On the other hand, when the throttle grip 5 is turned to the deceleration side in order to cancel a cruising state, a tension (pulling force) is applied to the portion of the cable 6 connected to the drum 72, because the throttle shaft 2 is biased by the negative pressure type actuator 10 through the throttle link 4, and the drum 72 will turn counterclockwise as illustrated in FIG. 4. In this case, since the portion of the cable 6 connected to the drum 71 is restrained from turning by the throttle drum 3, the drum 71 does not turn. Therefore, the torsion spring 73 is displaced by being pulled by the drum 72. When the displacement surpasses a predetermined amount, the switch 8 outputs a cancel signal, and the ECU 12 outputs a cruising state canceling instructions to the solenoid unit 11. A constant vehicle speed maintaining device similar to the above-described is disclosed in Japanese Patent Publication No. 3-44007.
In the constant vehicle speed maintaining device as described above, the cancel detector 7 is disposed, for example, on the cable 6, and is located between the throttle grip 5 and a carburetor 1. However, the cable 6 must be laid out to take into consideration the steering requirements of the steering handle in the case of a motorcycle, so that degree of freedom in the layout is extremely small. Under such a limited degree of freedom, the layout of the cable 6 and the layout of the cancel detector 7 is not easy.
In addition, since the cable 6 for regulating the throttle opening is bisected by the cancel detector 7, friction in the areas of the cable connection is increased. Further, since the layout of the cancel detector 7 is difficult as mentioned above, the cable 6 is not always laid out in the appropriate location, so that friction between the cable 6 and its casing increases. An increase in friction causes an increase in throttle load and an increase in the play in the connection areas. This increased friction can impair the operation characteristics, namely, the response performance of the acceleration and deceleration to the operations on the throttle grip.
It is an object of the present invention to provide a constant vehicle speed maintaining device which solves the above-mentioned problems of the prior art, can be easily mounted on a motorcycle with minor requirements concerning the layout, and can enhance the operational characteristics of the vehicle.
In order to attain the above object, the present invention is characterized by providing a throttle opening control means for controlling the throttle opening by a turning torque of a throttle grip. A DC servo-motor is provided for maintaining the throttle opening at a current vehicle speed in response to a constant vehicle speed maintaining instruction. A load detecting means is provided for detecting the load on the DC servo-motor when the DC servo-motor is operating in response to the constant vehicle speed maintaining instruction. A control means is provided for stopping the operation of the DC servo-motor and canceling the cruising state when the load on the DC servo-motor as detected by the load detecting means has varied.
In addition, the invention is characterized by providing a control means that cancels the cruising state when the load variation is not less than a predetermined amount and has continued for a predetermined period.
Further, the invention is characterized by providing a control means that cancels the cruise state when a load variation due to a turning torque in a decelerating direction on the throttle grip is detected.
Accordingly when the throttle grip is turned where the servo-motor is operating in response to the constant vehicle speed maintaining instruction, the throttle opening is going to vary regardless of the operation of the servo-motor, so that the load on the servo-motor varies. As a result, the load detected by the load detector varies, and the control means stops the operation of the servo-motor and cancels the cruising state.
According to the present invention, the turning of the throttle grip can be accurately detected. In addition, the cruising state may be canceled in response only to the rider""s clear cruise canceling action by turning the throttle grip in the direction for decelerating the vehicle. Therefore, in an accelerating operation, the vehicle is smoothly accelerated to perform a lane change or the like.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.